MILWAUKEE - Thirty years ago,
they weren't even mentioned in textbooks
on human evolution.

Today, researchers say,
the bonobo
(pronounced bow-NO-bow), the last of the great apes discovered by
Western
science, is starting to rewrite those textbooks, along with many of our
basic assumptions about human nature.

"The bonobo shows the
flexibility in
our lineage that we didn't know we had before," says Frans de Waal, a
prominent
investigator at the Yerkes
Regional Primate Research Center in Atlanta
and professor of psychology at that city's Emory University. "They're
female-centered,
egalitarian, have no cooperative hunting and substitute sex for
aggression."

After 20 more years of
research, predicts
De Waal, the bonobo "is going to change the whole picture of human
evolution."

Right now, though,
Barbara Bell is
more interested in getting them to behave. As a keeper/trainer for the Milwaukee County Zoo,
she works daily with the largest group of bonobos
(5 males and 4 females, ranging in age from 3 to 48 years) in North
America,
making it the second largest collection in the world (the largest can
be
found at the Dierenpark Planckendael, in Mechelen, Belgium). There are
only 120 captive worldwide.

"It's like being with
nine 2 1/2 year
olds all day," she says. "They're extremely intelligent."

Before she initiated a
positive-reward
training program with the bonobos three years ago -- the approach many
zoos use to train sea lions -- "there was no trust between us," Bell
says.
The apes would often scream loudly in their distinct, high-pitched
voices,
or try, usually with great success, to urinate on strangers visiting
their
holding pens in the basement of the zoo's Family of Apes of Africa
Pavilion
(Visitors in the public viewing area upstairs, by the way, are
protected
by glass).

"We had some very bad
behavior to contend
with," says Bell.

Teaching them to respond
to command
words, to willingly move from holding pen to holding pen, and present
parts
of their bodies for examination, has resulted in less stress for bonobo
and trainer alike, Bell notes.

Before training,
examining any bonobo
anatomy, usually required full anesthesia. Now, Bell can often do it
with
a simple request and a grape.

"They understand a
couple of hundred
words," she says. "They listen very attentively. And they'll often
eavesdrop.
If I'm discussing with the staff which bonobos (to) separate into
smaller groups, if they like the plan, they'll line up in the order
they
just heard discussed. If they don't like the plan, they'll just line up
the way they want."

"They also love to tease
me a lot,"
she says. "Like during training, if I were to ask for their left foot,
they'll give me their right, and laugh and laugh and laugh. But what
really
blows me away is their ability to understand a situation entirely."

For example, Kitty, the
eldest female,
is completely blind and hard of hearing. Sometimes she gets lost and
confused.

"They'll just pick her
up and take
her to where she needs to go," says Bell. "That's pretty amazing.
Adults
demonstrate tremendous compassion for each other."

The bonobo's apparent
ability to empathize,
in contrast with the more hostile and aggressive bearing of the related
chimpanzee, has some social scientists re-thinking our behavioral
heritage
-- especially the dominant male/submissive female scenario.

"The current model of
our progress
as a species uses the chimpanzee as the touchstone of human evolution.
Male dominance, aggression, cooperative hunting, warfare are all a part
of the story," says De Waal.

But as he wrote in his
1997 book, "Bonobo:
The Forgotten Ape": "Bonobo society seems ruled by the 'Make Love,
Not
War' slogan of the 1960s, rather than the myth of a bloodthirsty killer
ape that has dominated (evolutionary) textbooks for at least three
decades."

One reason we know so
little about
the bonobo today is that no one even knew the creature existed until
1929,
when its skull was discovered in a Belgian museum. Another reason for
our
ignorance is the animal's isolation. Its sole known habitat is the
remote
tropical rain forests of the Democratic Republic of Congo (formerly
Zaire)
in central Africa.

At first assumed to be a
slightly smaller
sub-species of chimpanzee, the bonobo was originally called a pygmy
chimp.
A few years after the Belgian discovery, however, the bonobo was
accorded
its place as a distinct species alongside the other great apes:
gorilla,
chimpanzee and orangutan.

The earliest study
comparing bonobos
and chimpanzees was carried out in the 1930s at Germany's Hellabrunn
Zoo
in Munich. The three bonobos used in the study, incidentally, were
so
terrified
by Allied bombardment of the city during the war, they died of heart
failure.

Among the differences
noted: The more
vocal bonobos are sensitive, lively and nervous, while chimps are
coarse
and hot-tempered; bonobos defend themselves by kicking with their feet,
while chimps pull attackers close and bite; a bonobo's voice contains
"a"
and "e" vowels, but chimps use more "u" and "o" vowels; and although
physical
violence is rare among bonobos, with chimps it's common.

Not much else was known
about bonobos
until the 1970s, when Japanese researchers became the first to venture
into their African habitat.

The ape's isolation,
combined with
longstanding despotism and political strife in the Democratic Republic
of Congo, deforestation and the killing of bonobos for food has not
only
limited subsequent field work but has jeopardized the animals'
survival.

Gay Reinartz,
coordinator of the Bonobo
Species Survival Plan for the Zoological
Society of Milwaukee County,
remains
hopeful, yet is deeply concerned. "We're on the edge," she says. "It
could
go either way."

In an effort to tip the
scales, Reinartz
is trying to raise $220,000 for a planned survey of the Congo's Salonga
National Park to determine the bonobos' distribution and conservation
status.
Researchers have estimated the total bonobo population at 5,000 to
20,000.

"What we do in this
country will make
a difference whether or not these guys live," Reinartz says. "I'm not
saying
I have all the answers, because it's a complex problem. But what we do
in terms of foreign policy, conservation and stimulating public demand,
will affect this species making it."

For Reinartz, bonobos
deserve to make
it "because they have their own special merits that have nothing to do
with the fact that we're related."

It's the animal's
relationship to humans,
though, that's causing all the interest.

Consider: The bonobo and
chimp are
equally close to us DNA-wise. Each shares more than 98 percent of our
genetic
material. As De Wall puts it: "That's about as close as a fox is to a
dog."

The bonobos' body
proportions, however,
compare more favorably than any other living ape to the 3.2
million-year-old
skeletal remains of Australopithecus afarensis, that transitional
creature
between ape and man that anthropologists named Lucy.

While resembling a
chimp, the bonobo's
body "immediately strikes us as more gracile and elegant," says De
Waal.
"The body is more slim and slender, the head is small and sits on a
thin
neck and narrow shoulders." Consequently, he says, when you see a
bonobo stand or walk upright, you can't help but feel you've been
there.

About 6 million years
ago, the human
lineage split off from the rest of the primate family tree. Three
million
years ago, the bonobo went its separate way. The chimp, you could say,
is still riding our common evolutionary tree trunk today.

Because researchers
believe the bonobo
may never have left its ancestral rain forest, they reason that it may
have changed less during its evolution than the chimpanzee, which is
thought
to have physically adapted as its environment changed. Of the bonobo,
chimpanzee
and man, "the bonobo may more closely resemble the common ancestor of
all
three modern species," De Waal says. "It's an important issue that's
yet
to be resolved."

Since De Waal's book was
published,
the issue that seems to have gotten the most attention is the animal's
overt sexuality. It's hard to ignore.

Zoo observations
suggest, on the average,
that every male, female and child bonobo engages in some form of
heterosexual,
homosexual or self-sexual activity every 1 1/2 hours. Adult rape, or
any
sexual abuse of an infant, however, has never been recorded in
captivity
or the wild.

"From what I've read in
the popular
press, it's gotten a little blown up," Bell says protectively. "You'd
think
they do it every 10 minutes."

But it's not the
frequency that seems
to startle people, Bell says; it's the too-human-for-comfort mode of
the
behavior.

For example, the frontal
orientation
of the bonobo's genitalia makes it one of only a handful of animals
able
to copulate face-to-face. And, as with humans, sex is usually engaged
in
for reasons other than procreation.

For bonobos, sex means
everything from
"hello" to "How about dinner?" De Waal calls it their "social balm."

When females embrace --
which is often
in this female-controlled community -- "it's called a GG rub," says
Bell.
"Genital-to-genital stimulation. It's like, 'Hello, how are you? I
haven't
seen you in a while.' "

The public, however,
usually doesn't
get it. "We get some pretty grossed-out parents," Bell says.

And the bonobos --
especially the males
-- seem to enjoy grossing them out. "They like to put their butts up to
the glass because it gets such a great reaction."

"When Lomako, a
13-year-old male, is
in rare form, he masturbates. Usually it's when he sees uniforms, when
there are 30 Brownies or Girl Scouts out front," says Bell with a sigh.
"He doesn't know it's taboo; he just gets a reaction."